Spectroscopic evidence of coexistence of clusters based on low (α) and high temperature (β) GeS2 crystalline phases in glassy germanium disulfide matrix

Technologically modified g-GeS₂(TiVj) glasses prepared by melt quenching from different temperatures (T_i) and with different cooling rates (Vj) were studied using Raman spectroscopy and model calculations. Differential Raman spectra {I_RGeS₂(T_iV₁)-I_RGeS2(T₂V₁)} showed the splitting of the main, most intensive wide-band, centered at 340 cm^-1. The position of the peaks found in the differential Raman spectra near 340 and 360 cm^-1 and position of the main vibrational modes in the ordinary Raman spectra of low- and high-temperature crystalline phases (α-, β-GeS2) were found to be in good agreement. Vibrational spectra of 4- and 6-member ring fragments selected from crystalline structure of β-GeS₂ were also determined using model calculations. Based on rings composed of GeS₄ tetrahedrons connected by corners and edges the structural interpretation of the vibrational bands of g-GeS₂(TiVj) at 360, 370 and 433 cm^-1 in their Raman spectra was performed. The existence of homopolar Ge-Ge and S-S “defect” bonds in the structure of germanium disulfide glasses was proved by formation of 5-member rings. Formation of fragments of both low- and high-temperature α-, β-GeS₂ crystalline phases in the structure of g-GeS₂(TiVj) glasses indicates the existence of mixed medium-range ordering in g-GeS₂.